In the past, grinding wheels have been held in place upon the supporting member by pouring molten sulfur, lead or other suitable material between a turned in flange and the wheel itself. The wheel is slightly enlarged in diameter at its supporting position so the molten material will hold it more firmly in place and prevent it from being accidentally withdrawn. This method is disclosed in U.S. Pat. No. 1,814,587.
Another method of holding the abrasive member to a plate is by means of a layer of specially processed material, usually rubber, which acts as a cushion to relieve grinding strains and shock. Additionally, where heavy stress and torque loads are encountered, wire and other suitable binding is placed on the outside diameter. This method is also used on soft grade, low strength wheels.
There are many well-known methods for producing particulate materials of varying particle size. Typical of these methods are simple mechanical choppers such as the Cumberland chopper. However, the Cumberland chopper is limited to production of comparatively high particle sizes and maintenance costs are high. Another industry practice is the use of cryogenic grinding involving liquid nitrogen or carbon dioxide and mechanical means for size reduction of the cold brittle particles. This method, while technically feasible, has generally been found too costly for general purpose size reduction. Another practice is the use of two roll grinders. In this system, material to be reduced in size is fed between the nip of two metal rolls having serrated surfaces. Particles fed to the roll mills are reduced in size by the stretching and tearing action imparted by the rolls. After passing through the rolls, the resulting particles are screened to desired Particle size but particle sizes are typically limited to 40-50 mesh.
Still another method that has been utilized is that of wet grinding such as disclosed in U.S. Pat. No. 4,049,588. In this patent, vulcanized rubber is converted into finely divided particles by pre-swelling the rubber, with a swelling fluid, forming a dispersion of the swollen particles and then comminuting the dispersed, swollen particles. U.S. Pat. No. 4,046,834 describes a wet grinding method in which an aqueous mixture of rubber particles is passed between two discs, one of which is rotating and the other stationary.
While aqueous grinding of particles between two grinding discs produces finely ground particles, this method has had the disadvantage of low production rates because stones of sufficient diameter to permit efficient production have not had sufficient strength to withstand stresses incurred at high speeds. The weakness of molded stone grinding wheels is suggested in U.S. Pat. No. 3,615,304 of which I am co-inventor. This patent discloses a method for preventing stone grinding discs from disintegrating which comprises the use of a fiberglass and resin band around the circumference of the wheel.
Accordingly, it is an object of this invention to provide a method for mounting bonded abrasive grinding discs on a high speed grinding mill.
Another object of this invention is to provide a mounting method for grinding discs that cannot be conveniently placed over the end of a rotating shaft. This aspect of my invention permits the grinding discs to be sectioned into two or more pieces before mounting.
Still another object of this invention is to provide a means for comminuting vulcanized rubber, plastics or other organic materials with stone grinding discs operating at high speeds. Other objects of this invention will become apparent to those skilled in the art after consideration of the following more detailed disclosure.